This invention relates to a method for regulating a compressor installation with at least one compressor element and, in the pressure conduit thereof, at least one cooler, at least one water separator and a dryer of the type comprising a pressure vessel with a drying zone and a regeneration zone, a rotor rotating in this pressure vessel, which rotor is filled with a regenerable drying agent, whereby the compressor element is driven by an electric motor, a portion of the compressed air delivered by this compressor element is branched off in the cooler before being cooled, is supplied, by means of a branch, towards the regeneration zone and, after cooling down and separation of the condensed water, is fed back to the pressure conduit, and whereby the rotor in the dryer is continuously rotated by means of an electric motor, such that the drying agent is continuously moved from the drying zone to the regeneration zone and back to the drying zone.
Compressor installations provided with an adsorption dryer are described, for example, in the patent documents U.S. Pat. No. 5,385,603 and GB-A-1.349.733.
In these compressor installations, the compressor element as well as the rotor are continuously driven at the same speed.
This means that the flow rate delivered by the compressor element remains constant or varies only within certain limits.
Increasingly, however, use is made of energy-saving compressor installations, whereby the flow rate delivered by the compressor element is adjusted to consumption. The compressor element thus is driven at a varying speed in function of said flow rate, as a result of which the power consumed by the motor of the compressor element can be restricted to a minimum.
This is achieved, for example, by driving the compressor element by an electric motor which is controlled by a frequency converter.
As the flow rate may vary within a broad range of 20% to 100%, these energy-saving compressor installations can not comprise a dryer of the aforementioned type. With a low flow rate delivered, the flow rate through the regeneration zone is too small to allow for a sufficient regeneration of the drying agent within the period of time during which the latter is present in the regeneration zone.
Due to the high dew point, an insufficient regeneration results in a shorter service life of the dryer.